Electric unit.



F. M. FURBE R. ELECTRIC UNIT. APPLICATION FILED JUNEZB, 1915.

Patented Apr. 10, 1917.

STATES PATENT OFFICE- I'EEDEBICK M. FURBER, OI REVERE, MASSACHUSETTS, ASSIGNOR TO UNITED SHOE MACHHQ'ERY COMPANY, OF PATERSON, NEW JERSEY, A CORPORATION OF NEW JERSEY.

ELECTRIC UNIT.

Specification of Letters Patent.

Original application filed February 19, 1915, Serial No. 9,343. Divided and this application filed June 28,

, 1915. Serial No. 36,721.

To all whom it may concern:

Be it known that I, FREDERICK M. FURBER, a citizen of the United States, residing at Revere, in the county of Suffolk and State of Massachusetts, have invented certain Improvements in Electric Units, of which the following description, in connection with the accompanying drawings, is a specification, like reference characters on the drawings indicating like parts in the several figures.

This invention relates. to electric heating units of general utility, although herein.

shown as embodied in an edge setting machine disclosed in my pending application Serial No. 9,343, filed February 19, 1915, of which the present application is a division.

Heretofore when electric units have been used in situations where they are subjected to severe shocks or vibrations it has been found that they deteriorate rapidly and that the repeated stresses to which they are thus subjected lead to their destruction in a short time.

It has been found advisable to provide electric units with a metal support, and such support necessarily expands under the influence of the heat developed by the unit and in the units heretofore used loosens its engagement with the weaker parts of the unit, permitting the destruction of the unit when subjected to violent and rapidly recurring shocks.

Great difliculty, too, has been experienced, due to the breaking of the resistance wire where its ends are fastened. This wire is very small, and in the units heretofore constructed, has been fastened at its ends in" a manner involving some form of more or less sharn bend. This,-of course, puts one side of the wire in tension and the other side under compression, and when such units are used in situations where they are subject to rapidly recurrin shocks, which, in themselves, as is well own, tend strongly to produce disorganization of molecular arrangement, the non-homo eneity of intermolecular stress at the ben produced by the she curvature there causes the wire to yie'l rapidly to this disorganizin tendency, with the result that it soon brea s.

. tion 0 A further disadvantage of units heretofore constructed is that paste or cement is used to hold in position their various parts, and this material cracks or powders under rapid vibration, so that the elements of the unit become loose, and short-circuiting and mechanical destruction result.

Another disadvantagemf units heretofore used is that they are so complicated in construction that when damaged by even the simplest injury to which they are subject, namely short circuiting, they cannot be repaired on the spot, and the cost of repair is prohibitive.

An object of the present invention is to provide a unit which shall not be subject to the disadvantages of units heretofore wire may be fastened thereto without the creation of substantially sharply varying o r asymmetrical inter-molecular stresses in the wire.

A further feature of my invention comprises a unit the elements of which are compacted and held together solely by a substantial mechanical pressure.

Another feature of my invention comprises an-elastic stress absorbing member by which variations in the pressure exerted by the supporting member of a heating unit are absorbed. j

A further feature of my invention is a unit so constructed and arranged that a burned out wire can be quickly and easily replaced.

These and other features of the invention comprising various combinations and arrangements of parts will be best understood and ap reciated from the followin descripg) a preferred embodiment t ereof semachine showing the unit in elevation;

Fig. 2 is an enlarged elevation of the unit partly in section on the line 2-2 of Fig. 1; and

\ 'Figs. 3, 4 and 5 are details showing themanner of fastening the ends of the resistance wire. I

The shaft 10 is oscillated rapidly on its xis in suitable bearings not shown. It caries the head 11 upon which is mounted the tool carrier 12', which supports the burnishing tools 13. The tool carrier 12 has a bore 14 in which is mounted the unit and which has a mica floor 14'. Slots 15 in the walls of the upper end of the bore 14 permit the egress of the lead wires.

The unit is built up on a nickel steel rod 16, having a head 17 at one end. To this head is brazed one of the flexible lead wires 18, which carries a lava bead 19, a number of glass beads 20 and the terminal 21. The lava head 19 rests in the. slot 15 and resists, better than a glass head, the intense heat at this point. x

Next to the head 17 on the rod 16, is mounted a mica washer 22, which is of larger diameter than the head 17, and just fits the bore 14. Next to the 'mica washer 22 is mounted.a lava ring 23, around which is placed the nickel steel terminal ring 24,

to which the other flexible lead wire 25 is brazed. The rings 23, 24 are of the same width, and the diameter of the ring 24 is less than that of the washer 22. Next on the rod 16 is located the lava core 25, which is of the same diameter as the terminal ring 24 and is helically threaded throughout its length. Next to the core is mounted in electrical contact with the rod 16, a nickel steel terminal 26 of the same diameter as the core, and next to the terminal 26 is mounted another mica washer 27, identical with the washer 22. Below this is mounted a steel washer 28 upon which the rod 16 is upset at 29.

The resistance wire 30 is wound in the helical thread, and fastened to its terminal elements 24, 26 in the manner shown in Figs. 3, 4 and 5. A slot 31 is cut in each of the elements 24, 26, the ends of the wire 30 are placed in the slots, and each of the lips 32 is then upset over the wire by a punch stroke, clamping it firmly in position.

The current flows through the wire 18, head 17, rod 16, terminal 26, wire 30, ring 24, to the wire 25. The washers 22, 27 proect beyond the outer cylindrical portions of the unit, and insulate it from the wallof the bore 14. The floor 14', insulates the end of the rod 16. The necessity of a cover or case for the unit is thereby avoided, and the heat is more easily and directly conveyed to the tools.

The lava used in the core 25 has a.,mean thermal coefficient of expansion "between F and 935 F., (just visible red) of 0000,0070 per 1 F., which is substantially that of steel. The nickel steel rod 16 used in the unit described has a mean thermal co-eflicient of expansion between the same limits of 0000,0076 per 1 F. The difference in co-eflicients of expansion between these limits per 1 F., is, therefore, 0.000,- 0006. long. The relative expansion of the steel rod and lava core in this unit when heated from 70 F to 930 F. would be, therefore,

(930 70) 2i 0.000,0006:0.0012 inch.

The rod 16 is so upset as firmly to compress the other elements of the unit between its ends. The mica washers 22, 27 are more compressible than the other elements mounted on the rod 16, and will safely take stresses due to the heading up of the rod 16, which might crush a more unyielding structure.

At the same time the washers are suff ciently elastic to take up the relative expansion,necessarily minute, as shown, of the nickel steel rod 16 and the lava core 25, when heated in use. The materials of the unit supported on the rod 16 are thus bonded together in a compact mass, always under a substantial compression. I have found that the lava coreis very resistant to shocks and that when it. does break, it breaks crosswise and not lengthwise. The longitudinal compression exerted by the rod 16 upon the core effectively precludes danger of breakage of this sort.

The means adopted for fastening the ends of the resistance wire avoids the heretofore experienced breakage of the wire at these points. The slot 31 is substantially in the prolongation of the helixin which the wire is wound on the unit, and the wire enters it without substantial bending. The upsetting of the sides of the slot on the wire applies a pressure to the wire which is substantially uniform circumferentially and progressively increases from zero to a maximum longitudinally, from the ends of the slot to its middle, so that sharp variations in molecular stress are avoided. It will be seen that in the unit shown, all the resistance wire is open to inspection and manipulation and that a burned out wire can be readily replaced by the operator, by merely spreading the slots 31 and upsetting them again.

I have found also that the use of nickel steel in the ring 24.- and the terminal 26 is of advantage, owing to the small tendency to corroslon evinced by this material. I have found that there is a great deal of corrosion, at the gunctlon of the resistance wires and The unit itself is about 2% inches H the elements to which their ends are fastened, in other units which I have examined and used. This disadvantage has been avoided by the construction shown.

Having described my invention, what I .claim as new, and desire to secure by United States Letters Patent is 1. An electric unit comprising a non-conducting core and an interior member supporting the core upon the structure with which the unit is associated, said member having substantially the same thermal coefficient of expansion as said core.

2. An electric unit comprising a lava core and an interior steel supporting member for said core.

3. An electric unit comprising a non-conducting core, a resistance wire carried thereon, and an interior member supporting the core upon the structure with which the unit is associated, said member having a thermal expansibility substantially equal to that of said core.

4. An electric unit comprising a non-conducting core, and an interior member supporting the core upon the structure with which the unit is associated, said member being substantially co-extensive with said core, said core and supporting member having substantially the same thermal co-eflicient of expansion.

5. An electric unit comprising-a non-conducting core, resistance wire carried on said core, terminal elements for said wire, said core and terminal elements being under resilient compression.

6. An electric unit comprising a non-conducting core, resistance wire carried thereby, a resilient member, and a support for said core and member constructed and ar ranged to maintain said parts under resilient compression.

7. An electric unit comprising a nonconducting core, a stress absorbing member and a support for said elements having substantially the same thermal co-efiicient of expansion as said core, said stress absorbing member being constructed and arranged to absorb the relative expansion of said support and core.

8. An electric unit comprising a supporting rod, two resilient elements mounted thereon, and a non-conducting core mounted on said rod between said elements, said rod being arrangedto compress the parts I mountedthereon. v

9. An electrical unit comprising a nonconducting core,. aterminal member at each end of the core having substantially the Copies 01 same peripheral contour as the core, and a very fine resistance wire wound on said core and supported by said core and terminal fmembers throughout its length, said terminal members provided with means for securing the ends of said wire without abrupt bending, whereby the tendency to disruption of the wire due to vibration or changes in temperature is reduced. '10. An electric unit comprising a non-conducting core provided with a helical groove,

terminal members at the ends of said core provided with slots lying substantially in the prolongation of said helical groove, and a resistance Wire wound in said groove with its ends in said slots.

11. An electric unit comprising a non-conducting core, a resistance wire carried by said core, a terminal member for said wire provided with a slot formed to receive the end of the wire, the middle portion of the slot being upset upon the wire.

12. An electric unit comprising a non-conducting core, terminal members, insulating members and a support, said elements being held together solely by a substantial mechanical compression.

13. In a resistance unit, the combination with an insulating body and a tenuous resistance element wound in a coil on said body, of a conducting member mounted at the end of said coil and having a surface substantially flush with the surface of said body, the wire at the end of said coil adjacent to said member being carried on to said member without bending the wire abruptly and secured to said member.

14. In a resistance unit, the combination with an insulating body and a resistance wire wound in a coil on said body, of a conducting member mounted atthe end of said coil and having a groove eiitending substantially parallel with the turns of said coil with the bottom of said groove lying substantially flush with the surface of said body at a point close to said body, the Wire at the end of said coil adjacent to said member being carried into said groove and secured therein without bending the wire abruptly between the coil and its point of connection with said member.

15. An electrical unit'having a non-conducting core, resistance wire carried on said core, and a terminal member for said wire having nickel in its composition.

In testimony whereof I have signed my name to this specification.

FREDERICK M. FURBER.

I this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. G. 

